{%- if page.header.theme == nil -%}
  {%- if layout.header.theme == nil -%}
    {%- assign __return = site.site_theme -%}
  {%- else -%}
    {%- assign __return = page.header.theme -%}
  {%- endif -%}
{%- else -%}
  {%- assign __return = page.header.theme -%}
{%- endif -%}